WASHINGTON (CNN) -- Security at financial sites in New York City, northern New Jersey and Washington, D.C., increased significantly Sunday after the Department of Homeland Security raised the terror threat level for those areas to orange, or high.

The potential targets include the International Monetary Fund and the World Bank in Washington, Prudential Plaza in Newark, New Jersey, and the Citigroup Building and New York Stock Exchange in New York.

As part of the enhanced security precautions, commercial traffic is prohibited from entering New York City via the Holland Tunnel starting at 12:01 a.m., Monday, according to the Port Authority of New York and New Jersey Web site.

Ridge said the plans appeared to include car and truck bombs, aimed at "the attempted physical destruction of these facilities."

Ridge also said "we're concerned about targets beyond these and are working to get more information about them."

"The quality of this intelligence, based on multiple reporting streams in multiple locations, is rarely seen and is alarming in both the amount and specificity of the information," Ridge told reporters at a news conference Sunday.

Raising the threat level in specific areas will make the buildings more secure and the people in them more aware, Ridge said.

But he said the intelligence lacked specific information about when the strikes might occur and did not indicate whether they were imminent.

Sunday's move was the first time the color-coded alert system had been applied to specific areas, though New York City has been on orange alert since the scheme was put in place after the terrorist attacks of September 11, 2001.

Ridge said the different approach was taken because "compared to previous threat reporting, these intelligence reports have provided a level of detail that is very specific."

The rest of the nation remains at threat level yellow, or elevated. Orange is the second-highest level, just above yellow and just below red.

In New York, a law enforcement source said the information that prompted the alert is so specific -- down to details about meeting rooms and parking structures -- that it appears surveillance might have been conducted inside the buildings.

They said it includes details about whether security guards are armed, the location of security cameras, notes on traffic patterns and possible escape routes, building construction details, what kind of explosives could do maximum damage, the configuration of parking garages, what kind of vehicles are allowed, and even the incline of garage entrances.

Although not offering specifics about the sources of the information, Ridge said most of them "are the result of offensive intelligence and military operations overseas, as well as strong partnerships with our allies around the world, such as Pakistan."

The White House said the information that prompted Sunday's decision to raise the threat level developed during the past 72 hours.

It said President Bush was briefed on developments while on a weekend campaign swing in Ohio and Pennsylvania. He signed off on raising the threat level Sunday morning.

Both the World Bank and IMF -- which are across the street from each other in downtown Washington, just a few blocks from the White House -- said they would be open for businesses as usual Monday morning, albeit with additional security measures in place.

Washington police Chief Charles Ramsey said security around the IMF, the Federal Reserve, and the Bureau of Engraving and Printing had been beefed up.

Capitol police are on 12-hour shifts and have increased patrols in the Capitol Hill neighborhood, spokeswoman Sgt. Contricia Ford said.

Although the specific threats may be elsewhere in Washington, Ford said the Capitol police would cast a wide security net.

"It's a small city, so a threat to one part is a threat to the whole," she said.

Prudential told its employees to report for work as scheduled Monday, a spokesman said, and the company is increasing security at all of its locations in northern New Jersey.

In New York, representatives from 12 security firms, including those handling security for the New York Stock Exchange, Citigroup and Morgan Stanley, were briefed on the threat Sunday by New York Police Commissioner Ray Kelly, a law enforcement source said.

Kelly said monitoring of trucks entering the city would be stepped up.

Building security directors have been urged to safeguard the heating, air conditioning and ventilation systems from being used to deliver biological or chemical weapons, he said.

But Kelly, speaking at a news conference Sunday, played down a possible threat from chemical weapons:

"Explosives are considered more likely at this time."

New York Mayor Michael Bloomberg said security for the Republican National Convention, which begins August 30 in Madison Square Garden, had been increased.

"We are deploying a full array of counterterrorism resources. We will spare no expense, and we will take no chances," Bloomberg said. "We will be watching and protecting the city through never-ending vigilance."

Kelly said he first learned of the information Friday. He and other officials studied it over the weekend to "try to ascertain its validity, its seriousness, make sure it wasn't a hoax by one person."

Bloomberg said the targets could be a deliberate attempt by terrorists to deceive authorities into focusing their resources on the targets, thereby leaving other targets vulnerable to attack.

He said it was not clear when the information was gathered.

"Some of this information could have been collected over the last few years," he said.

City officials have been considering activating the National Guard as the Republican convention approaches, Bloomberg said, adding that officials began been weighing that idea before they received word of the threat.

Ridge said in early July that al Qaeda was planning a large-scale attack in "an effort to disrupt the democratic process" before Election Day on November 2.